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At least 19 recordsLinked to original sources
PubMed1975

The fate and migration of microfilariae of a Guatemalan strain of Onchocerca volvulus in Simulium ochraceum and S. metallicum, and the role of the buccopharyngeal armature in the destruction of microfilariae.

The migration and fate of microfilariae of a Guatemalan strain of Onchocerca volvulus in Simulium ochraceum and S. metallicum was studied. The anatomical distribution of microfilariae at various times after ingestion was recorded from a study of histological sections of the flies. S. ochraceum showed higher microfilarial intakes than S. metallicum which is probably attributed to an inherent difference in their ability to ingest. The migration of microfilariae out of the mid-gut took place essentially through the expanded part (the stomach). Despite the high microfilarial intakes by S. ochraceum, only a few microfilariae were able to migrate successfully into the thorax (2.6%) whereas in S. metallicum showing a low microfilarial intake, a higher rate of migration was noted (74.5%). The main bulk of microfilariae ingested by S. ochraceum died and disintegrated in the stomach. This was due to the presence of a well-developed cibarial armature in the buccopharyngeal apparatus of S. ochraceum in contrast to S. metallicum where such an armature is lacking. Microfilariae were severely damaged by the cibarial teeth while en route to the stomach. They rapidly underwent profound changes in morphology and staining properties and were often surrounded by clusters of the phagocytic leucocytes in the blood mass. In some flies, microfilariae, apparently damaged, were still entangled in the cibarial teeth 5 minutes to 3 hours after taking a blood-meal.

Animals↗
PubMed1977

The microfilaria of Brugia timori (Partono et al. 1977 = Timor microfilaria, David and Edeson, 1964): morphologic description with comparison to Brugia malayi of Indonesia.

The microfilaria of Brugia timori was compared with microfilariae of Indonesian strains of periodic and subperiodic Brugia malayi using alcohol-fixed (stained) and formalin-fixed (unstained) preparations. As noted by other observers of the Timor microfilaria, the absence of a stained sheath in Giemsa preparations, a long cephalic space with a length-to-width ratio of about 3:1, and a great overall body length are features which most readily distinguish this parasite. Additionally, B. timori has greater numbers of single row nuclei in the terminal column of body cells and a lesser bulge of the cuticle surrounding nuclei in the distal portion of the tail than does B. malayi. About 60% of B. timori microfilariae were exsheathed in haemalum-stained thick blood films. Brugia timori microfilariae were found to be distinct from microfilariae of B. malayi by comparing percentages of total body length included between the cephalic tip and major internal anatomic markers.

Animals↗
PubMed1978

[Experiments in vitro with Litomosoides carinii (Nematoda: Filarioidea). I. Maintenance of adult females and microfilariae as well as release of microfilariae in different culture media (author's transl)].

Embryos of L. carinii continue intrauterine development to microfilariae and are totally released into the medium within 5--6 days when the latter (Tc 199) is changed daily and air is used as the gas phase. Oogenesis or further fertilization of eggs, however, does not occur in vitro in any of the media examined by us. One female releases 140 X 10(3) microfilaria/day on an average in vitro within 5--6 days. Mean initial numbers of 300 X 10(3) Mf/female/day are observed. Addition of equine serum inhibits microfilarial release in vitro; normal cotton rat serum prolongs survival of females while total numbers of released microfilariae or retained embryonic stages are not increased. The serum of post-patent animals does not influence the numbers of released microfilariae or their viability or survival of females. Microfilariae released in vitro in Tc 199 + 33% normal cotton rat serum survive for more than 8 days, when air is used as the gas phase and the medium is changed daily. Microfilariae isolated from the blood of patent animals survive for at most 6 days, at a 48-hourly change of medium survival does not even exceed 4 days.

Animals↗
PubMed1985

Immunity to Litomosoides carinii in Mastomys natalensis. I. Effect of immunization with microfilariae and existing primary infections on the parasitaemia after microfilariae injection and challenge infection.

Subcutaneous injections of intrauterine stages of Litomosoides carinii into Mastomys natalensis induced strong immunity to i.v. injected blood microfilariae. Immunity, developed after boostering with an i.p. and an i.v. injection of microfilariae, did not totally suppress the parasitaemia of a challenge infection but reduced significantly the microfilaraemia level. No effect was found on number and size of the worms of the challenge infection, the number of microfilariae or the number of leucocytes in the pleural cavity. Delayed type hypersensitivity reactions in challenged animals were similar to those in non-immunized, infected controls. Sera of immunized animals agglutinated microfilariae and mediated cell attachment to microfilariae. Challenge infections did not change this until the end of the fourth week post infection but sera taken 32 days after challenge and later failed to induce such reactions. Challenge infections performed 120 or 240 days after a primary infection did not increase the parasitaemia of recipients. Dissections carried out 130 days after the challenge showed that (a) the developmental rate of the challenge infection was reduced by about 50%; (b) the size of the challenge parasites was reduced; and (c) that these worms produced significantly less embryonic stages in comparison to worms of primary infections, of which about 90% were abnormal.

Agglutination Tests↗
PubMed1976

Transmission of microfilariae and infective larvae of Dipetalonema viteae (Filarioidea) among vector ticks, Ornithodoros tartakowskyi (Argasidae), and loss of microfilariae in coxal fluid.

During studies on the acquisition and transmission of infection with the filaria Dipetalonema viteae by Ornithodoros tartakowskyi, it was found that young nymphs and starved medium-sized ticks feed on recently engorged larger ticks. In this manner young ticks acquired the infection with microfilariae, and the microfilariae thus taken developed normally and after 30 days of development were transmitted to a jird. Ticks harboring infective larvae were able to transfer them to other engorged ticks when attempting to feed on them. Although it is not known whether this occurs in nature, it could be a supplementary mechanism in the natural maintenance of this species of filaria. Ticks eliminated microfilariae in the coxal fluid in small numbers during the 1st hr after the infective meal and in increasing numbers with time, reaching a peak between 3 and 5 hr. This mechanism may prevent some ticks from becoming hyperinfected.

Animals↗
PubMed1990

Acid phosphatase activity in microfilariae of Setaria labiato-papillosa and comparison with other blood microfilariae of dog and horse origin.

Acid phosphatase activity was demonstrated in smears of Setaria labiato-papillosa microfilariae by the naphthol AS-TR-phosphate method. The staining was restricted to 3 distinct sites, corresponding to the excretory pore, the inner body and the anal pore. This staining pattern was compared with those of Dirofilaria immitis, Dirofilaria repens and a Setaria of horse origin.

Acid Phosphatase↗
PubMed1985

Brugia malayi: intravenous injection of microfilariae in ferrets as an experimental method for occult filariasis.

Microfilaremia, immune responses, and pathology were compared in ferrets infected with 100 third-stage larvae of Brugia malayi (subperiodic strain) or injected intravenously with 10(6) microfilariae. Ferrets (Mustela putorius furo) inoculated with third-stage larvae typically became patent during the third month after infection, with a mean patency of 123 +/- 25 (SE) days. Ferrets injected intravenously with microfilariae exhibited a relatively constant microfilaremia for 3-4 weeks and usually cleared microfilariae before the fourth month. Ferrets that cleared microfilariae after intravenous injection of microfilariae or after infection with third-stage larvae failed to become patent or became amicrofilaremic within 3 weeks after a challenge intravenous injection of 10(6) microfilariae. Clearance of circulating microfilariae was associated with eosinophilia and serum antibody specific for the microfilarial sheath in ferrets injected with microfilariae and in most ferrets infected with third-stage larvae. Ferrets infected with third-stage larvae and necropsied after clearance of microfilariae had tissue inflammatory reactions to microfilariae characteristic of occult filariasis (tropical eosinophilia) in man; these ferrets exhibited immediate cutaneous hypersensitivity and circulating reaginic antibody to antigens of microfilariae. In ferrets necropsied following two intravenous injections of microfilariae, the majority of ferrets examined within 10 days after clearance of microfilariae had visible liver lesions to microfilariae identical to those of the ferrets infected with third-stage larvae; immediate cutaneous hypersensitivity and reaginic antibody were not consistently detected in ferrets injected with microfilariae. Sera from ferrets that had cleared circulating microfilariae were transferred passively into ferrets made microfilaremic by intravenous injection of microfilariae. Sera with microfilarial sheath-reactive IgG antibody titers (greater than or equal to 1:200) and microfilarial agglutination titers (greater than or equal to 1:40) rapidly cleared injected microfilariae (less than 24 hr); this serum also cleared or greatly reduced circulating microfilariae established by an infection with third-stage larvae; only the IgG-containing fraction of the sera was active in immune clearance. Sera that cleared microfilariae of B. malayi did not clear circulating microfilariae of Dirofilaria immitis or prevent recurrence of circulating microfilariae of B. malayi in ferrets infected with adult filariae.(ABSTRACT TRUNCATED AT 400 WORDS)

Agglutinins↗
PubMed1989

Onchocerca gutturosa and Onchocerca lienalis in cattle: variation in length of microfilariae by site of recovery.

Dermal microfilariae recovered from specimens obtained from umbilical and cervical sites of cattle infected with adult Onchocerca gutturosa alone or with adults of O gutturosa and O lienalis were measured and compared with uterine microfilariae obtained directly from gravid female worms of each species. Uterine microfilariae of O gutturosa were longer than dermal microfilariae obtained from cattle harboring only adults of O gutturosa. Dermal microfilariae were recovered from umbilical and cervical sites in these cattle. Those found at the cervical site had lengths equal to or greater than lengths of microfilariae recovered from the umbilical site. There was a significant (P less than 0.0001) shift in length across populations of microfilariae of O gutturosa from various sites in its bovine host, with a progressive decrease in length between microfilariae recovered from the worm's uterus, microfilariae from the cervical dermis, and microfilariae from the umbilical dermis, respectively. A similar direct comparison was not possible for microfilariae of O lienalis, because none of the cattle was infected with only adult worms of this species. In an indirect comparison, microfilariae of O lienalis were identified at the umbilicus, but their presence in the cervical region could not be determined unequivocally because of confounding of microfilariae length by concurrent infection with O gutturosa. Uterine microfilariae from O lienalis were longer than uterine microfilariae of O gutturosa, although a degree of overlap in the range of measurements existed between species.

Algorithms↗
PubMed1979

Brugia malayi microfilaraemia in mice: a model for the study of the host response to microfilariae.

Microfilariae of Brugia malayi were obtained from the peritoneal cavities of infected gerbils and were then injected intravenously into mice. A sub-periodic, nocturnal microfilaraemia was produced. The level of microfilaraemia was proportional to the number of parasites injected, with approximately 1-3% of microfilariae being found in the peripheral circulation. The duration of microfilaraemia was proportional to the number of parasites injected; it subsided by 30 days after injection of 104 microfilariae but was still present at a low level 120 days after injection of 2 x 105 microfilariae. A transient splenomegaly developed after injection of microfilariae. Histopathological examination revealed large numbers of microfilariae free in the lumens of pulmonary small blood vessels and without any accompanying inflammatory reaction. Lesser numbers of microfilariae were seen in the cardiac blood and hepatic and renal blood vessels for the first few days after injection. There was cellular proliferation in the splenic white pulp and vascular congestion of the red pulp. Microfilariae labelled with 51Cr were injected intravenously; 57% of radioactivity was found in the lungs, 8.5% in the liver and 2.9% in the spleen. Mice developed immediate hypersensitivity reactions to B. malayi antigen by 4 weeks after injection, but Arthus and delayed hypersensitivity reactions were not seen at any time. when mice which had been injected 5 months previously were challenged with a 2nd injection of microfilariae, there was an accelerated clearance of parasites over 2 weeks and a marked peripheral blood eosinophilia developed. In contrast with natural infections, in which the continuous production of microfilariae complicates assessment, this model provides a system in which factors controlling the circulation of microfilariae in the bloodstream can be studied independently.

Animals↗
PubMed1975

Factors influencing the passage of Onchocerca volvulus microfilariae into the urine.

The effect of various substances on the output of Onchocerca volvulus microfilariae in the urine was investigated in volunteers infected with the Cameroon forest and Sudan-savanna strains of the parasite. Output of microfilariae in the urine tended to be higher during periods of normal activity than during sleep. During waking hours, the rate of output remained generally steady, but in some patients occasional showers of microfilariae appeared in the urine, possibly associated with the intake of food and drink. Drinking 1.2-2.5 litres water produced a shower of microfilariae in the urine of some subjects. This began within an hour of drinking and its onset preceeded that of the diuresis. Thiazide diuretics, acting on the convoluted tubules, produced no increase in microfilaruria. In savanna subjects intravenous injection of DT TAB vaccine caused pyrexia, and simultaneously large numbers of microfilariae appeared in the urine. There was no associated diuresis, and no increase in the concentration of microfilariae in the venous blood. In forest subjects DT TAB caused no increase in microfilaruria. In all subjects 25-50 mg diethylcarbamazine (DEC) caused large numbers of microfilariae to appear in the urine on day 0, within a few hours of the first dose; and there was an increased output of urine over the first 24 hours. Microfilaruria declined sharply on day 1 of treatment, but in subjects developing a high microfilaraemia, it rose again on day 2, and declined more slowly thereafter. Betamethazone, given in conjunction with DEC, appeared to slow the rate of destruction of microfilariae in the skin and lymph glands, and to prolong the duration of microfilaraemia and microfilaruria. The findings suggest that there is a reservoir of microfilariae in the glomerular capillaries, which fills slowly by accumulating microfilariae from the circulating blood. The microfilariae probably enter the urine by penetrating the glomerular capillary.

Adult↗
PubMed1986

Longevity of microfilariae following removal of the adult worms.

The present study was undertaken to determine the longevity of a population of microfilariae in a natural host following the removal of the adult worms without drug intervention. Four squirrel monkeys previously infected with Dipetalonema gracile were allowed to develop stable microfilaremias. All adult worms were then removed surgically from the peritoneal cavity. Weekly microfilaria counts were made on each animal and the decline in microfilariae recorded. At the time of adult worm removal, microfilaremias ranged from 750 to 12,500 mf/ml. The observed decline in microfilaria densities was gradual, but steady, in all animals. Microfilariae persisted in 1-ml blood samples for 60, 62, 91, and 101 weeks following removal of adult worms. The results indicate clearly that in a naturally produced population, in a natural definitive host, microfilariae survive for 60 to 100 weeks. The gradual decrease in microfilarial densities would appear to be the result of the death of specific batches or broods of microfilariae. The microfilariae which persisted in the blood the longest undoubtedly represent those which were produced just prior to the removal of the adult worms. It is postulated that because of the long life-span of microfilariae, female worms are not called upon to produce a continual supply of microfilariae, nor is the need for mating as frequent as might be expected. Equally important, the number of microfilariae which the host is called upon to phagocytize is considerably smaller than previously suggested.

Animals↗
PubMed1979

Studies on Dipetalonema viteae (Filarioidea) 3. Antibody-dependent cell-mediated destruction of microfilariae in vivo.

Antibody-dependent cell-mediated destruction of Dipetalonema viteae microfilariae could be demonstrated in the golden hamster using a micropore chamber technique. Microfilariae were eliminated within 24 hours in chambers of 3.0 and 5.0 microm pore size when implanted into amicrofilaremic hamsters (week 30 post infection). At peak microfilaremia (week 12 post infection), only some hamsters could efficiently destroy microfilariae. In chambers with 0.3 microm pore size, microfilariae survived for more than 3 weeks in all hamsters. In uninfected hamsters, microfilariae could only be eliminated if they had been preincubated with serum or its 19S fraction containing antibodies to the cuticle of microfilariae. The opsonizing activity of the serum was abolished by 2-mercaptoethanol treatment. The composition of cells adhering to microfilariae was always significantly different from the composition of cells which migrated into a chamber. The adhesion patterns on individual microfilariae indicated that no single effector cell type was responsible for the destruction of microfilariae. The eosinophil was the predominant cell type but neutrophils, lymphocytes and monocytes also adhered to the microfilariae. Cellular adhesion led to the immobilization of microfilariae and subsequently to their disintegration within large cell clusters. During the final stages of destruction the contribution of the monocyte became more pronounced.

Animals↗
PubMed1979

The exsheathment of Brugia pahangi microfilariae under controlled conditions in vitro.

Two reproducible techniques for the exsheathment in vitro of microfilariae of Brugia pahangi, and other sheathed microfilariae, are described. Microfilariae were isolated from infected cat blood by filtration and suspended in Hank's Balanced Salt Solution. The first technique involved the incubation of isolated microfilariae for one hour in 20 mM CaCl2 in a phosphate-free Balanced Salt Solution, during which time approximately 90% of the microfilariae lost their sheaths. The second method of exsheathing microfilariae of B. pahangi involved exposure of microfilariae to solutions of endopeptidase (5.8 units/ml) or papaya extract protease (3.0 units/ml) in Ca2+-free HBSS. Exsheathment rates of 95--100% occurred within 30 minutes in both enzyme solutions. Both the Ca2+ ion and the endopeptidase technique have proven equally effective in stimulating exsheathment of microfilariae of Brugia malayi, Wuchereria bancrofti and Litomosoides carinii. Such artificially exsheathed microfilariae are used for in vitro cultivation studies. The viability of Ca2+- and endopeptidase-exsheathed microfilariae of B. pahangi has been confirmed by inoculation of exsheathed larvae into susceptible female mosquitoes.

Aedes↗
PubMed1988

Comparative densities of Wuchereria bancrofti microfilaria in paired samples of capillary and venous blood.

Concurrent finger-prick and venous blood samples were obtained from 43 patients infected with Wuchereria bancrofti. Microfilariae were counted in blood smears and on nuclepore filters. Based on the numbers of microfilariae in 20-microliters finger-prick samples, an expected (theoretical) number of microfilariae in venous samples was calculated. This expected value was compared to the actual number of microfilariae present in venous blood. The actual number of microfilariae present ranged from 0.7 to 30 times (median 3) less than expected. The exponential function y = 16.74e.17x, r2 = .69, where y = venous counts and x = capillary counts was found to accurately reflect the relationship between venous and capillary counts. Each unit (microfilaria) change in capillary blood would result in an expected 19% unit increase/decrease in venous blood. The results support strongly the theory that microfilariae are unevenly distributed in the blood system. The epidemiological implication is that persons with low or ultralow microfilaremia levels in venous blood may have a much greater pool of microfilaria available in capillaries. We believe that the present study explains, at least partially, why mosquitoes feeding on these kinds of microfilaria carriers (frequently) have a greater uptake fo microfilariae than expected.

Adolescent↗